title: Na(+)-dependent, active and Na(+)-independent, facilitated transport of formycin B in mouse spleen lymphocytes.
abstract: Na(+)-dependent, active and Na(+)-independent facilitated nucleoside transport were characterized in mouse spleen cells using rapid kinetic techniques and formycin B, a metabolically inert analog of inosine, as substrate. The Michaelis-Menten constants for formycin B transport by the two transporters were about 30 and 400 microM, respectively. The first-order rate constant for Na(+)-dependent transport was about 4-times higher than that for facilitated formycin B transport. The Na(+)-dependent carrier is specific for uridine and purine nucleosides and accumulates formycin B concentratively in an unmodified form. Concentrative accumulation was inhibited by ATP depletion and gramicidin and ouabain treatment of the cells. Our data indicate a single Na(+)-binding site on the Na(+)-dependent nucleoside carrier and a Michaelis-Menten constant for Na+ of about 10 mM. This transporter was not significantly inhibited by dipyridamole and nitrobenzylthioinosine, inhibitors of the facilitated transporter. The Na(+)-independent, facilitated nucleoside transporter of spleen cells exhibits properties comparable to those of the carriers present in mammalian cells in general. The B lymphocytes remaining after depletion of spleen cell populations of T lymphocytes by incubation with a combination of T-cell specific monoclonal antibodies plus complement exhibited about the same activities of active and facilitated nucleoside transport as the original suspension.
authors.affiliation: Department of Microbiology, Medical School, University of Minnesota, Minneapolis 55455.
authors.forename: P G
authors.initials: PG
authors.lastname: Plagemann
authors.forename: J M
authors.initials: JM
authors.lastname: Aran
authors.forename: C
authors.initials: C
authors.lastname: Woffendin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics*; D001692:Biological Transport; D002478:Cells, Cultured; D004176:Dipyridamole / Q000494:pharmacology; D005573:Formycins / Q000493:pharmacokinetics*; D008214:Lymphocytes / Q000378:metabolism*; D051379:Mice; D009705:Nucleosides / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013154:Spleen / Q000166:cytology / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D005573:Formycins; D009705:Nucleosides; C034561:formycin B; D010042:Ouabain; D004176:Dipyridamole; D000255:Adenosine Triphosphate; D012964:Sodium; D013936:Thymidine